Filters are generally known. Filter elements can be provided that are inserted into the filler such as in the form of filler bags. Typically, the filler bags each comprise a wire cage on which a bag of filter material is mounted. The filler bags are suspended from a horizontal partition wall and extend downwards into a dust chamber to which the dust-containing gas or air is supplied and conveyed upwards across the partition wall through the filler bags. Hereby the dust particles deposit on the filler bag and drop down to the bottom of the filter housing from where they can be removed.
The same applies when other types of filler elements are used, be it bag fillers, as mentioned, but other fillers may also be concerned where filler material is attached to a kind of holder means. For instance, they may be filter cartridges, but any suitable filter material can be used.
When the dust-containing gas is supplied to the dust chamber opposed to the filler elements, a certain wear occurs on the filler elements, in particular the filler elements that are located most proximate the inlet. It was attempted to solve the problem of wear in Danish patent No. 175107 B1 by arranging a number of diffuser elements in the inlet part outside the filler housing, see patent disclosure DK 175107 B1.
However, the solution has a limitation with respect to the amount of product taken through the filter. In case of large amounts of product wear will occur—even in case diffuser elements are used.
What is usually taken through the filler is a flow of gas. The flow of gas is often atmospheric air, but in some cases it may be a kind of gas or a mixture of kinds of gases containing particles that are separated off the flow of gas in the filler. Thus, a product may be entrained in a flow of gas, which product is separated off in the filler, or particles may be involved that are undesirable in a flow of gas and are hence separated off.
Thus, it may be the gas or gases in the flow of gas which constitute a final or partial product or it may be the product that is separated off.
It may thus also be purified air or purified gas from flue gas or the like it is desired to accomplish.
In the following the term gas flow is used to designate the flow and the term gas is used in general. The product most often being particulate, the product will, in the following, be referred to as particles; however, obviously, the term particles is to be construed in its widest sense. The problem of having large amounts of particles in the gas is that the particles cause relatively much wear on e.g. the filter elements. This is typically solved by use of a pre-separator, e.g. in the shape of a cyclone.
A technique is known wherein gas and product are conveyed into the filter underneath the filter elements. Hereby the effect is accomplished that the major part of the product is separated off underneath the filter elements and drop down to the outlet of the filter. Thereby it is avoided that the particles that are contained in the gas flow are conveyed directly onto the filter elements.
However, this solution is associated with the drawback that a relatively large, upwardly oriented flow of gas passes between the filter elements which makes it difficult to clean the filter elements, the dust having to settle against the gas flow to leave the filter. In practice this means that a much larger filter than usual is to be applied to provide an upwardly oriented gas rate between the filter elements which is so low that the dust is able to drop against the gas flow.